The semiconductor industry continues to strive for continuous device miniaturization that is driven by the need for mobile and high-performance systems in emerging industries such as autonomous vehicles, virtual reality, and future mobile devices. To accomplish this feat, new, high-performance materials are needed to circumvent inherent engineering and physics issues encountered in the rapid reduction of feature sizes in microelectronic devices.
Ideally, thin-films of metal would be deposited using thin-film deposition techniques such as Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) owing to their inherent ability to deposit material in a high-throughput, conformal, and precise fashion.
Chemical vapor deposition (CVD) is one of the most common deposition processes employed for depositing layers on a substrate. CVD is a flux-dependent deposition technique that uses precise control of the substrate temperature and the precursors introduced into the processing chamber in order to produce a desired layer of uniform thickness. The reaction parameters become more critical as substrate size increases, creating a need for more complexity in chamber design and gas flow technique to maintain adequate uniformity.
A variant of CVD that demonstrates excellent step coverage is cyclical deposition or atomic layer deposition (ALD). Cyclical deposition is based upon atomic layer epitaxy (ALE) and employs chemisorption techniques to deliver precursor molecules on a substrate surface in sequential cycles. The cycle exposes the substrate surface to a first precursor, a purge gas, a second precursor and the purge gas. The first and second precursors react to form a product compound as a film on the substrate surface. The cycle is repeated to form the layer to a desired thickness.
The advancing complexity of advanced microelectronic devices is placing stringent demands on currently used deposition techniques. Unfortunately, there are a limited number of viable chemical precursors available that have the requisite properties of robust thermal stability, high reactivity, and vapor pressure suitable for film growth to occur. Additionally, metal precursors often use oxygen or an oxidizing co-reagent for deposition. Use of oxygen and oxidizing co-reagents can be incompatible with adjacent films in the device stack. Therefore, there is a need in the art for metal precursors and co-reagents that react to form metal and metal-based thin films, and metal precursors that can form metal films without an oxidizing co-reagent.